Vertical Access LLC
AIA CES Presentations

Mechanical Anchor Strength in Historic Masonry Materials
1 AIA Learning Unit

Description
The current lack of codes, guidelines or recommendations for pull-out and shear values of mechanical anchors in historic masonry materials leaves the design community to improvise the design and specification of these anchors. Guidelines available are most relevant to concrete and brick masonry. Although field-testing is employed for some projects, more commonly an arbitrary reduction of the ultimate yield values is used when designing these elements for use in natural stone. The creation of a standard or empirical design equation for these values is arduous because, unlike concrete and concrete masonry units, historic building stone units are not manufactured in a controlled environment, and their physical properties such as density and compressive strength vary from quarry to quarry and within quarry strata.

A testing program to evaluate two types of mechanical fasteners in both limestone and sandstone for pull-out and shear will be described in this course. The ultimate yield strength is correlated to both compressive strength and surface hardness of the sample stone. Stone quality was evaluated in situ using ultrasonic pulse velocity measurements. Pulse velocity is sensitive to stone density, stiffness, and flaws that may have a corresponding effect on anchor capacity. Development of a relationship between anchor capacity and stone characteristics, as measured using the ultrasonic pulse velocity approach, would permit classification of field-installed anchors requiring destructive pullout tests.

Learning Objectives

• Review the needs for structural anchors used in masonry materials and review the various mechanical and adhesive anchor alternatives


• Learn about relevant existing research on mechanical and adhesive anchor strengths in historic masonry materials.


• Learn how to design an on-site testing program to empirically determine appropriate design strengths.


• Review challenging case studies of designing anchorages in historic masonry materials such as terra cotta book tile, marble, granite, limestone and sandstone.